Cryogenic liquid storage containers



Sept. 21, 1965 J. M. CANTY ETAL CRYOGENIC LIQUID STORAGE CONTAINERS Filed Oct. 20, 1961 INVENTORS JOHN M. CANTY VINCENT E. FIRST RICHARD J. FRAINIER A T TORNEV United States Patent 3,207,353 CRYOGENIC LIQUID STORAGE CONTAINERS John M. Canty, Vincent E. First, and Richard J. Frainier,

Tonawanda, N.Y., assignors to Union Carbide Corporation, a corporation of New York Filed Oct. 20, 1961, Ser. No. 146,523 4 Claims. (Cl. 220-45) This invention relates to cryogenic liquid storage apparatus and particularly to mobile, thermally-insulated cryogenic liquid storage containers.

The present day, conventional method of storing cryogenic liquids comprises storing such liquids in doublewalled, vacuum-insulated storage containers. As the desired volume of liquid to be stored in one body is increased, the problem of supporting the inner product liquid vessel within the protective outer shell becomes more and more acute. The strength of the inner vessel support structure depends in part upon the size and number of the members thereof and, for relatively large storage containers, the conduction of atmospheric heat through the support structure into the product liquid may become a sizable proportion of the total atmospheric heat inleak therein. This problem is particularly troublesome in connection with mobile storage containers of the size employed in highway trailers and railway tank cars. Not only must the static weight of the inner vessel be supported, but provision must be made for forces experienced by the inner vessel because of accelerations, decelerations, and shocks due to bumps which the moving container undergoes. These forces necessitate employing stronger and hence larger support structures.

Heat inleak through the support structure may be compensated to a certain extent by employing more efiicient insulation between the inner vessel and the outer shell. However, when the valuable transported liquid has a very low atmospheric boiling temperature, such as does liquid hydrogen or helium, the problem created by heat inleak through the support structure becomes extremely critical and cannot be countered sufficiently by merely increasing the efliciency of the insulation. Means must be found to restrict this heat inleak through the support structure in order .to minimize the loss of storage liquid by excessive evaporation thereof.

It is, therefore, a primary object of this invention to provide a support structure for the inner vessel of a cryogenic liquid storage container which contributes to the total ambient heat leakage into the inner vessel to a much smaller degree than conventional inner vessel support structures. A further object is to provide an inner vessel support structure that is stronger and more stable than prior art structures.

These and other objects and advantages of the present invention will become apparent from the following detailed description thereof together with the accompanying drawings in which:

FIG. 1 is a horizontal, partially sectional view of a storage container illustrating the principles and novel features of this invention;

FIG. 2 is a view of a section taken on the line 22 of FIG. 1; and

FIG. 3 is a view in section of one end of another storage container illustrating the principles and novel features of this invention.

In general, the inner vessel support structure of this invention comprises a plurality of re-entrant tubes which are joined to the wall of the inner vessel at their outer ends and extend thereinto. The inner ends of the re-entrant tubes are gas-tightly sealed from the interior of the inner vessel and the outer ends thereof are open to the insulation space defined between the inner vessel and the outer shell thereby providing gas communication between the 3,207,353 Patented Sept. 21, 1965 interiors of the re-entr-ant tubes and the insulation space. A plurality of load rods, the outer ends of each being joined to the outer shell of the storage container, extend into respective re-entrant tubes and are joined at their inner ends to the walls of such re-entrant tubes. The reentrant tubes and the respective load rods are preferably employed in cylindrical containers wherein they are positioned in transverse planes transverse to the longitudinal axis of the container with at least two such load rod-reentrant tube combinations being positioned in each of the aforementioned transverse planes.

It is preferred that the re-entrant tubes and the respective load rods be inclined from the vertical at an angle based upon the resultant of the transverse forces acting upon the inner vessel, and preferably disposed at right angles to the longitudinal axis of the storage container. Such an arrangement is shown in FIGS. 1 and 2, which will be described in detail subsequently.

The inner vessel support structure is best adapted for employment in horizontally positioned cylindrical storage containers and will be described herein in conjunction with such a container. It should be understood, however, that other container configurations are also suitable, such as, for example, spherical and oval-shaped containers, and that this invention is not limited to employment only in cylindrical containers.

Furthermore, the low heat leak characteristics of this inner vessel support structure are most useful in containers storing such valuable cryogenic liquids as liquid hydrogen, neon, and helium. Consequently, the insulation space is preferably substantially completely filled with highly efficient insulation such as the opacified type and evacuated to a low positive pressure below about microns of mercury absolute. Of course, other liquids may be stored in containers employing this support structure and other insulation such as powder-in-vacuum and straight vacuum may be used in conjunction therewith. But, inasmuch as this invention is most useful when employed in liquid hydrogen, neon, and helium service, where highly elficient insulations are required, it will be described in conjunction therein.

FIGS. 1 and 2 illustrate one embodiment of the inner vessel support structure which suspends an inner vessel 10 from outer shell 12. Insulation space 14 between outer shell 12 and inner vessel 10 is preferably substantially completely filled with opacified insulation.

The term opacified insulation as used herein refers to a two-component insulating system comprising a low heat conductive radiation permeable material and a radiant heat impervious material which is capable of reducing the passage of radiant heat without significantly increasing the thermal conductivity of the insulating system.

As more fully described and claimed in copending US. application Serial No. 597,947, filed July 16, 1956, in the name of L. C. Matsch, now US. Patent No. 3,007,596, the low heat conductive material may be fibrous insulation which may be produced in sheet form. Examples of such a material include a filamentary glass material such as glass wool and fiber glass, preferably having fiber diameter less than about 50 microns. Also such fibrous materials preferably have a fiber orientation substantially perpendicular to the direction of heat flow across the in sulation space. The spaced radiation-impervious barriers may comprise either a metal, metal oxide, or metal-coated material, such as aluminum-coated plastic film or other radiation reflective or radiation adsorptive material or a suitable combination thereof. Radiation reflective material comprising thin metal foils are preferably suited in the practice of the present invention. For example, reflective sheets of aluminum foil having a thickness between 0.2 mm. and 0.002 mm. may be employed. When fiber sheets are used as the low-conductive material, they may additionally serve as a support means for the relatively fragile radiation-impervious sheets. For example, it is preferred that an aluminum foil-fiber sheet insulation be spirally wrapped around inner vessel 10 with one end of the insulation wrapping in contact with inner vessel 10 and the other end nearest outer shell 12 or in actual contact therewith.

It will be appreciated that other forms of opacified insulation may be used. For example, the radiation impervious barriers may be incorporated directly into the low heat conductive material as described and claimed in US. Patent No. 2,967,152 issued in the name of L. C. Matsch et a1. Such opacified powder vacuum type insulation might comprise, for example, equal parts by weight copper flakes and finely divided silica. The latter material has a very low solid conductivity value but is quite transparent to radiation. The copper flakes serve to markedly reduce the radiant heat inleak.

Even though the previously described preferred opacified insulation is more effective than straight vacuum insulation at higher internal pressure (poorer vacuum), its effective thermal insulation life is extended if the pressure can be maintained at or below a desired level such as, for example, below about 100 microns of mercury absolute. A gas removing material such as an adsorbent may be used in insulation space 14 to remove by adsorption any gas entering through the joints of the cryogenic container. In particular, crystalline zeolitic molecular sieves having pores of at least angstrom units in size, as disclosed in US. Patent No. 2,900,800 issued in the name of P. E. Loveday, may be employed as the adsorbent in accordance with the teachings therein since this material has extremely high adsorptive capacity at the temperature and pressure conditions existing in insulation space 14 and is chemically inert toward any gases which might leak into such insulation space. The adsorbent material may be provided within insulation space 14, for example, by intermixing the same with the insulation or by placing it in the inner vessel support structure in a manner to be described subsequently.

The preferred inner Vessel support structure for horizontally disposed containers shown in FIGS. 1 and 2 comprises at least two sets of inclined re-entrant vessel tubes 16 and 18, and 17 and 19, each set being located in an adjacent plane, parallel to the plane of the other and transverse to the longitudinal axis of storage container 20. Each re-entrant tube preferably extends through inner vessel 10. At the respective re-entrant tube inner ends 22 and 24, and 23 and 25 respectively, the same are preferably sealed gas tightly and joined to inner vessel by means such as welding. The open outer ends of the reentrant tubes, at 26 and 28, and 27 and 29 respectively, are welded gas tightly in openings in the wall of inner vessel 10 thereby providing gas communication between the interiors thereof and insulation space 14.

In this embodiment, load rods 30 and 32, and 31 and 33 respectively, extend from outer shell anchoring means 35 and 37, and 39 and 41, wherein they are connected to such means, through insulation space 14 and the interiors of their respective re-entrant tubes to the end portions thereof where they are connected to inner vessel anchor ing means 35a and 37a, and 39a and 41a, respectively. The load rods are secured to outer shell anchoring means 35 and 37, and 39 and 41, respectively, and to inner vessel anchoring means 35a and 37a, and 37a and 39a respectively by suitable methods known to those in the art. For example, the load rods may be threaded at each end and connected by adjusting nuts to the respective inner and outer anchoring means.

Re-entrant tubes 16 and 18, and 17 and 19 in the embodiment of FIGS. 1 and 2, could be extended just past the storage container longitudinal axis and then terminated. However, by extending them to the opposite side of inner vessel 10, they provide added rigidity to inner vessel 10 in the transverse direction. Furthermore, by placing a screen or similar gas permeable material across the inner vessel ends 22 and 24, and if desired, across inner vessel ends 23 and 25, of re-entrant tubes 16 and 18, and 17 and 19 respectively, the aforementioned adsorbent material could be placed within these lower portions of the tubes. Inasmuch as the adsorbent material placed therein would be at all times in thermal contact with the liquid storing portion of inner vessel 10, the adsorbent would be conditioned to operate most efiiciently. Another suitable location for the adsorbent material would be within a blister 11 attached to the lower portion of the inner vessel.

The inclination of the re-entrant tubes and the load rods therein from the vertical is based upon the resultant of the transverse forces applied to the inner vessel. Of course, more than one pair of adjacent transverse planes containing an inner vessel support structure is necessary to provide adequate inner vessel support. The number and spacing of such planes involves design considerations, but, in most cases, two such pairs of planes each located near an outer end of the container will ordinarily provide adequate supporteven for storage containers of the size of highway trailers or railroad tank cars.

T-o suspend the inner vessel 10 from outer shell 12 as shown in FIGS. 1 and 2, the load rods are assembled in stressed relation so that they are always in tension; the set comprising load rods 30 and 32 tending to pull the inner vessel upward and the set comprising load rods 31 and 33 tending to pull the inner vessel downward. It is preferred that circumferential support members 34 and 36 be aifixed to the outer shell in the planes of load rods 30 and 32, and 31 and 33 respectively, in order to equalize the stresses experienced by the outer shell due to its support of inner vessel 10. Any other suitable external support structure can be used such as that disclosed in U.S. Patent 2,256,679 to H. C. Korneman and G. H. Zen-ner.

The relative lengths of the load rods of this invention are especially critical. They must be longer than the radius of the inner vessel 10 and, further, must not be radially oriented with respect to such inner vessel. As previously noted, all of the load rods are stressed in tens-ion and therein lies the importance of the relative lengths of the load rods. If the load rods, for example, were the same length as the radius of inner vessel 10 and were connected at the center of the inner vessel on its longitudinal axis of rotation, the following stress pattern would be created in each load rod: first there would exist the stress created by support of the inner vessel and its contents; second there would exist the stress created by the contraction of the inner vessel and the corresponding re-entrant tube upon cool-down caused by the low temperature of its contents; third there would exist the stress created by the temperature gradient along the length of each load rod from its cold inner end to its warm outer end. All of these stresses are cumulative, that is, they are experienced in the longitudinal direction of each load rod. In the type of container that the present invention will find its greatest utilitynamely, containers the size of highway trailers or railway tank cars-the cumulative effects of these stresses would necessitate the employment of strong compression springs or such large diameter load rods that the heat leak advantages accruing from the use of long load rods would be more than offset by the necessarily large heat leak path provided by the increased load rod diameter necessary to resist such large contraction stresses.

By employing load rods that are not radially positioned and have lengths greater than the radial length of the inner vessel, the effects of the aforementioned stresses are vectorially additive rather than being arithmetically additive in a direct cumulative sense. Therefore, the cross-sectional area of such load rods may be markedly less than the diameter required by prior art apparatus which experiences cumulative stresses. For example, for non-radial load rods having lengths about the diameter of the inner vessel, and thermal contraction coefficients substantially identical to the inner vessel thermal contraction coeflicient, no stress increase will occur in the load rods on cool-down of the inner vessel. A secondary but most important advantage in employing nonradial load rods is that there exists no problem of preventing rotation of the inner vessel relative to the outer shell because of sloshing of the stored contents during movement of the container. The positioning of the load rods of the present invention automatically prevents such a rotation tendency.

The inner vessels of the mobile storage containers depicted in FIGS. 1-2 are prone to longitudinal movement caused by acceleration and deceleration of the storage container, inasmuch as the preferred inner vessel support structures depicted therein do not completely restrict such movement. A preferred method of counteracting the tendency of the inner vessel to move axially longitudinally under the above-mentioned conditions comprises a re-entrant tube-load rod support structure, similar in many respects to those shown in FIGS. 1-2 located at one end of the storage container and positioned either in line with the longitudinal axis or parallel to the longitudinal axis thereof. The load rod is preferably constructed to prevent relative longitudinal movement of the inner vessel whether such be forward or backward. Alternately, the load rod may be inclined to the horizontal and also more than one may be employed to support the inner vessel longitudinally. The length to which this inner vessel end support structure extends into the inner vessel depends on the length of the heat leak path required to maintain the heat influx along this path below a predetermined value, as well as the amount of metal cross section needed to accomplish the desired column strength.

It will be understood that modification-s and variations may be effected Without departing from the scope of the novel concepts of the present invention. For example, if the transversely positioned inner vessel support structures depicted in FIGS. 12 are also inclined with respect to the longitudinal axis of the storage container such as is shown in FIG. 3, the longitudinal support structure could be eliminated. In this embodiment, at least two sets are inclined opposingly to each other in planes oppositely inclined to the transverse. As in the preferred embodiment of FIGS. 1 and 2, for horizontally disposed containers, two such pairs each located near an outer end of the container will provide adequate support for the inner vessel.

What is claimed is:

1. In a double-walled cylindrical and horizontally disposed cryogenic liquid storage container comprising an inner product liquid holding vessel, an outer shell surrounding the inner vessel thereby forming an insulation space therebetween, and means for fillin g, discharging, and venting said inner vessel, inner vessel support means for supporting said inner vessel from said outer shell comprising at least two sets of load rod-re-entrant tube structures each structure being positioned in a transverse plane parallel to the other, the structure positioned in one such plane extending downward from said outer shell and connecting to the lower section of said inner vessel, and the structure positioned in an adjacent parallel transverse plane extending upward from said outer shell and connecting to an upper section of said inner vessel, each structure comprising a plurality of inner vessel re-entrant tubes inclined to the vertical and transversely extending nonradially into said inner vessel and having an inner end sealed from the interior of said inner vessel and joined to said inner vessel and an open outer end gas tightly joined to the rim of an opening in the wall of said inner vessel such that the interior of each re-entrant tube is in gas communication with said insulation space and a plurality of transversely positioned load rods each extending through the interior of the corresponding re-entrant tube and each having an outer end connected to said outer shell and an inner end connected to an inner end portion of a corresponding re-entrant tube, said load rods being assembled in stressed relation so as to support said inner vessel in tension, there being at least two load rods positioned in each of said transverse planes.

2. Inner vessel support means according to claim 1 and including longitudinal inner vessel support means for controlling axial movement of said inner vessel.

3. Inner vessel support means according to claim 2 wherein said longitudinal inner vessel support means comprises at least one inner vessel re-entrant tube and load rod support structure having a re-entrant tube extending into said inner vessel and having an inner end sealed from the interior of said inner vessel and an open outer end gas-tightly joined to the rim of an opening in the wall of said inner vessel such that the interior of said re-entrant tube is in gas communication with said insulation space and a load rod extending through the interior of said re-entr-ant tube and having an outer end connected to said outer shell and an inner end connected to the inner end portion of said re-entrant tube, such structure being aligned horizontally along the longitudinal axis of the storage container.

4. In a double-walled cylindrical and horizontally disposed cryogenic liquid storage container comprising an inner product liquid holding vessel, an outer shell sur rounding the inner vessel thereby forming an insulation space therebetween, and means for filling, discharging, and venting said inner vessel, inner vessel support means comprising at least two sets of inner vessel re-entrant tube and load rod support structures each structure being positioned in a transverse plane which is opposingly inclined to the horizontal such that adjacent transverse planes intersect, the structure positioned in one such plane extending downward from said outer shell and connecting to the lower section of said inner vessel, and the structure positioned in an adjacent oppositely inclined transverse plane extending upward from the said outer shell and connecting to an upper section of said inner vessel, each structure comprising a plurality of inner vessel re-entrant tubes inclined to the vertical .and transversely extending non-radially into said inner vessel and having an inner end sealed from the interior of said inner vessel and joined to said inner vessel end and an open outer end gas-tightly joined to the rim of an opening in the wall of said inner vessel such that the interior of each reentrant tube is in gas communication with said insulation space and a plurality of transversely positioned load rods each extending through the interior of the corresponding re-entrant tube and each having an outer end connected to said outer shell and an inner end connected to an inner end portion of a corresponding re-entrant tube, said load rods being assembled in stressed relation so as to support said inner vessel in tension, there being at least two load rods positioned in each of said transverse planes.

References Cited by the Examiner UNITED STATES PATENTS 1,522,886 1/25 Heylandt 2209 X 2,528,780 11/50 Preston 220l5 X 2,587,204 2/52 Patch 22015 2,592,974 4/52 Sulfrian 22015 2,940,631 6/60 Keeping 220l4 2,986,011 5/61 Murphy 22015 X THERON E. CONDON, Primary Examiner.

GEORGE O. RALSTON, Examiner. 

1. IN A DOUBLE-WALLED CYLINDRICAL AND HORIZONTALLY DISPOSED CRYOGENIC LIQUID STORAGE CONTAINER COMPRISING AN INNER PRODUCT LIQUID HOLDING VESSEL, AN OUTER SHELL SURROUNDING THE INNER VESSEL THEREBY FORMING AN INSULATION SPACE THEREBETWEEN, AND MEANS FOR FILLING, DISCHARGING, AND VENTING SAID INNR VESSEL, INNER VESSEL SUPPORT MEANS FOR SUPPORTING SAID INNER VESSEL FROM SAID OUTER SHELL COMPRISING AT LEAST TWO SETS OF LOAD ROD RE-ENTRANT TUBE STRUCTURES EACH STRUCTURE BEING POSITIONED IN A TRANSVERSE PLANE PARALLEL TO THE OTHER, THE STRUCTURE POSITIONED IN ONE SUCH PLANE EXTENDING DOWNWARD FROM SAID OUTER SHELL AND CONNECTING TO THE LOWER SECTION OF SAID INNER VESSEL, AND THE STRUCTURE POSITIONED IN AN ADJACENT PARALLEL TRANSVERSE PLANE EXTENDING UPWARD FROM SAID OUTER SHELL AND CONNECTING TO AN UPPER SECTION OF SAID INNER VESSEL, EACH STRUCTURE COMPRISING A PLURALITY OF INNER VESSEL RE-ENTRANT TUBES INCLINED TO THE VERTICAL AND TRANSVERSELY EXTENDING NONRADIALLY INTO SAID INNER VESSEL AND HAVING AN INNER END SEALED FROM THE INTERIOR OF SAID INNER VESSEL AND JOINED TO SAID INNER VESSEL AND AN OPEN OUTER END GAS TIGHTLY JOINED TO THE RIM OF AN OPENING IN THE WALL OF SAID INNER VESSEL SUCH THAT THE INTERIOR OF EACH RE-ENTRANT TUBE IS IN GAS COMMUNICATION WITH SAID INSULATION SPACE AND A PLURALITY OF TRANSVERSELY POSITIONED LOAD RODS EACH EXTENDING THROUGH THE INTERIOR OF THE CORRESPONDING RE-ENTRANT TUBE AND EACH HAVING AN OUTER END CONNECTED TO SAID OUTER SHELL AND AN INNER END CONNECTED TO AN INNER END PORTION OF A CORRESPONDING RE-ENTRANT TUBE, SAID LOAD RODS BEING ASSEMBLED IN STRESSED RELATION SO AS TO SUPPORT SAID INNER VESSEL IN TENSION, THERE BEING AT LEAST TWO LOAD RODS POSITIONED IN EACH OF SAID TRANSVERSE PLANES. 